Introduction:

Norway has a low prevalence of methicillin-resistant Staphylococcus aureus (MRSA), with a rate of less than 1% of all staphylococcal infections. Reports from the Norwegian Notification System for Infectious Diseases (MSIS) show an increase in the number of reported cases of MRSA from 63 in 1998 to 142 in 2002. Most cases are now contracted in Norway and outside hospitals. Although there have been several outbreaks of MRSA in hospitals, this is the first report of MRSA outbreaks in Norwegian nursing homes (NH).

Material/methods:

Since March 2003 there has been outbreaks of MRSA at two different NH in Central Norway located 111 km from each other. The initial detection of MRSA was performed at a local hospital. Positive strains were sent to St Olav University hospital for confirmation and further investigation. Strains from 24 persons (Both infection and carrier strains) were analysed by Pulsed Field Gel Electrophoresis (PFGE), and one strain from each NH was analysed by Multi Locus Sequence Typing (MLST).

Results:

NH A had 10 cases among inmates and five among health care workers. NH B had nine cases, all among inmates. MRSA strains were isolated from nostrils or wounds, in some case from both locations. The nine cases in NH B had an identical PFGE pattern. The strains from NH A were also similar except from one band difference. The strains from NH A differed by one or two bands from the NH B strains, thus all strains were closely related using PFGE. By MLST both strains were found to be ST 45. The SCCmec gene has not yet been determined. (The international strains Berlin is ST 45 type IV)

Discussion:

No exchange of personnel or inmates had occurred between the two NH, and no obvious cause of spread was found. The close relation of the strains makes us suspect a common source. Although both NH are served by the same hospital, this hospital had not experienced any outbreak of MRSA. Our results show the potential for spread of MRSA within NH. Several authors report MRSA within NH to be an increasing problem, and NH residency has been proven to be an independent risk factor for MRSA carriage upon hospital admission. It is important that health care workers at NH are aware of this. Proper infection control must be implemented not only in hospitals but also in NH.